As Cameron said, the referendum is a once in a lifetime choice. If you vote to leave we will leave the Single Market, customs union, and ECJ (or words to that effect) and no mention of with or without a deal.
Also no mention of: OK if you vote to leave and we then spend the next two and a half years talking about 'crashing out over the cliff edge and into the no deal abyss' on all the mainstream media outlets in order to prevent that even being thought about as an option. And while all that's going on work secretly on giving away our bargaining power and coming up with the worst possible deal, and running the clock down in order to force a situation where we can ask you if you've changed your mind yet... no I really don't remember him saying that.
On the other hand every member of the Government knows the rules regarding votes of no confidence in the PM and the 1922 committee, so your comparison is incorrect
As I've said before, I always thought that Parliament would vote down a leave vote in the referendum, it wasn't a binary choice at all, just an elaborate charade. The public have been conned